The invention relates to a sensor with at least one field effect transistor (FET) having at least one semiconductor material.
The use of a field effect transistor, in particular of a metal oxide semiconductor field effect transistor (MOS-FET) as a sensor is known. Whereas, in a customary MOS-FET the electrical resistance of the transistor channel (gate) is controlled by means of a gate electrode insulated relative to the channel by an oxide layer an electrode of this kind is not provided in a FET sensor. In the use of the FET as a sensor the resistance of the transistor channel is influenced by the interaction with a sample to be investigated, whereby conclusions can be drawn relating to the nature of the sample, in particular the sample surface.
The use of a field effect transistor as an acceleration sensor is, for example, known from U.S. Pat. No. 4,873,871. In this connection a microbeam which can be deflected on acceleration of the sensor is arranged in the vicinity of the transistor channel such that when the microbeam approaches the transistor channel, or the microbeam is moved away from the transistor channel, the channel resistance correspondingly changes.
In U.S. Pat. No. 4,020,830 the use of a field effect transistor as a chemical sensor is disclosed. In this connection a membrane is applied onto an insulating layer of the transistor channel and is brought into contact with the surface of a sample to be investigated, for example a liquid. The membrane is designed such that it interacts selectively with a predetermined type of ions of the sample. The application of a voltage between the sample and the transistor results in an interaction between the membrane and the ions of the sample, which in turn leads to a change of the channel resistance of the transistor which allows conclusions to be drawn on the nature of the sample investigated.